In my experience law enforcement is reluctant; and often flat will not, release evidence – specially a firearm – without an Order from the Court or without some other legal disposition.
If your firearm was seized as evidence (or for any other reason), you need an Order from the Court or a Writ of Mandamus stating that your firearm shall be released back to you.
If you do not now have an Order from the Court, you can petition the Court pro per (person who represents himself / herself in a legal proceeding rather than have an attorney) to have the Court order law enforcement to release your firearm to you.
You can research how to do this online or contact the State BAR in your state for an attorney referral. Often, these attorneys will offer a free 5 – 10 minute consolation; or, just a very modest fee for a full 15 – 20 minute consolation.
If you do not get your Court Order, you will need a lot of luck getting your firearm back from law enforcement. Remember, the Sergeant that you are chasing does not care one twit if you get your gun back or not. Also, I am not so sure the Sergeant has the authority to release your handgun with a legal order to do so.
PS: If / when you do get your gun back, do not be surprised that it is damaged (to some degree).